Metal ship doors are generally designed to be watertight in relation to the frames on which they are respectively mounted. For this reason, provision has been made for providing these doors with systems for locking in the closed position which are such that the said doors can remain closed even in the event of accidental overpressure, so as to prevent the entry of water or air into the corresponding rooms.
European patent document EP-B-552 505 presents a locking system which is supposed to reliably ensure the watertightness of a ship door. According to a preferential example embodiment which is described in this document in relation to FIG. 3, this locking system is notably characterised by a high number of catches (six in number in the example depicted) so as to effectively guarantee the aforementioned locking. These catches are designed to conic into abutment against walls internal to the frame on which die door is mounted,
The system essentially comprises of two bars mounted vertically on a door leaf by means of the catches, which are respectively pivotally mounted on the leaf and articulated on each bar. These two bars are connected to each other and at their facing top and bottom ends by two horizontal arms, on which other catches are articulated. Each arm is connected by its ends to the corresponding ends of the bars, by means of two links articulated on the bars. Each link, this is pivotally mounted on the leaf.
A control handle designed to move the bars via a link to which it is connected and consequently to cause the catches to pivot about their respective pivots so as to release them from the frame. The handle is mounted so as to be connected with the bar which is furthest away from the leaf hinges.
A major drawback of such a locking system lies in the complexity of its manufacturing process.